While fuel injection systems have all but entirely replaced carburetors in automotive engines, the transition from traditional carburetors to fuel injectors in aircraft engines has been slower. Nonetheless, fuel injection systems have become very popular for aircraft engines because they provide greater performance, economy, and reliability.
Most prior art fuel injection systems used in aircraft engines are volume-air flow type systems, which are based on the principle of measuring air flow to establish correct fuel flow to the engine cylinders. These systems include a throttle body fuel injection servo which measures the amount of air moving past the throttle by use of a venturi. An in-line diaphragm type flow regulator then converts the air pressure from the venturi into a proportional fuel pressure. During normal operation of the aircraft engine, the position of the throttle controls the air flow through the fuel injection servo or to the regulator, which then controls the flow of fuel to the cylinders. The servo is the primary component used in the fuel injection system and performs all functions required to establish fuel flow volumes. The regulated fuel flow from the servo is sent to a fuel flow divider, which divides the steady stream of fuel into smaller streams of fuel, one for each cylinder. Fuel lines carry fuel from the divider to injector nozzles located in the intake ports of each cylinder. The injectors supply fuel to the intake manifold. Fuel then enters the cylinder from the intake manifold under the low pressure created in the cylinder during the intake cycle.
During normal operation of the aircraft engine, the position of the throttle and the air flowing through the fuel injection servo or flow regulator, controls the flow of fuel to the cylinders. As the throttle is opened, more fuel is delivered to each cylinder, resulting in an increase in the speed of the engine or in manifold pressure, and thus more power being generated by the engine. In certain circumstances, due to mechanisms that cannot be adequately modeled, operators of some fuel-injected aircraft engines have discovered that switching on the auxiliary or boost fuel pump when the aircraft is on the ground and the engine is set to idle or at a low power setting has caused a slight change in RPM and fuel flow reading fluctuations.
A fuel injection system which avoids the shortcomings attendant with the prior art devices and practices utilized heretofore is the subject matter of the present application.